Workers reduced water levels by 2 ½ feet behind a faltering reservoir dam in Mississippi that feeds Louisiana’s Tangipahoa River, authorities said Friday.
Officials have a four-fold approach to relieving pressure at the Tangipahoa Lake dam in Percy Quin State Park, Mississippi Department of Environmental Quality engineer Richard Harrell said.
“We’re continuing to drain the lake through normal spillway operations. We’re also using pumps to pump water out over the east side and continuing construction of the emergency breach on the west side,” Harrell said. “And the fourth thing is that we’re looking at our patch options for the two (mud) slides that caused the damage to the dam itself.”
The slides have shown no signs of further deterioration in the past 48 hours, giving officials “some comfort” that the earthen dam will continue to hold, he said.
The lake was at about 332.7 mean sea level, as of 3 p.m. Friday, and could be dropped another 3 feet through normal spillway operations, Harrell said.
Gov. Bobby Jindal said Friday evening the lake level had dropped to the point that the emergency spillway was no longer discharging and pressure on the dam had been reduced.
Once the water level has been reduced through normal spillway operations, workers will remove the plug from the intentional breach and, through a controlled flow, lower the lake another 6 to 8 feet, Harrell said.
“As for what that will mean for the downstream flow, there really should be little to no effect,” Harrell said. “The cut (breach) will have less discharge than what’s going through the spillway right now, so you shouldn’t see any additional effect there in Louisiana.”
Louisiana officials have been afraid the dam would fail, sending a huge amount of water down the Tangipahoa River and endangering people from Kentwood to Ponchatoula.
The Governor’s Office estimated such a flood could affect 40,000 to 60,000 people.
In response, the Louisiana National Guard task force commander was stationed at the Emergency Operations Center on Friday, Jindal said.
Overall, the Guard had 566 Guardsmen, one LUH-72 Lakota helicopter, 72 Humvees, 47 high-water vehicles, 142 buses for evacuation operations and four Zodiac boats stationed for the response effort in Tangipahoa Parish, Jindal said.
The Guard response force was staged at two locations and also provided a 10-man shelter security team at Ponchatoula High School, he said.
In addition, the state Department of Wildlife and Fisheries assembled a search and rescue response force consisting of 118 wildlife agents with vessels, 80 state Urban Search and Rescue personnel with 15 vessels, 10 Louisiana National Guardsmen with vessels and five state Department of Environmental Quality personnel, Jindal said.
The Louisiana Department of Transportation and Development also restaged buses to help with evacuations, with 153 en route or already having arrived in the affected areas as of Friday evening, Jindal said.
Tangi Pines Nursing Center in Amite, located about 3,900 feet from the Tangipahoa River, was evacuated to its sister facility in Gretna out of an abundance of caution, Jindal said.
The state Department of Health and Hospitals helped evacuate 140 patients and 110 caretakers using two coaches, four paratransit vehicles and 49 ambulances, he said. All but 11 patients went to Bayside, which had evacuated earlier to Tangi Pines due to a power outage that was later restored, he said.
The remaining 11 patients were taken to Hood Memorial Hospital, Jindal said.
Most of the residents within a half mile of the river evacuated Thursday, but many of them have started to return, Tangipahoa Parish President Gordon Burgess said late Friday morning.
“We would like for them to stay out at least 24 more hours,” Burgess said.
He said that would give workers a chance to further reduce the water levels in the reservoir.
There is still a danger that the dam will fail, he said.
Officials have estimated that a failure of the dam would increase flooding along the river by 2 feet.
The water being released from the lake is running into a wetland area and eventually will find its way to the Tangipahoa River, but that will be a slower process, Burgess said.
That will give the Tangipahoa River a chance to drain and lower flood levels, Burgess said.